WPDang says that Lenovo has sent a number of R&D executives to meet with Microsoft in an attempt to negotiate more freedom for designing the UI of a Lenovo Windows Phone 8 model. For the recently launched Android powered Lenovo LePhone S880, the OEM had spent plenty of time and money on the UI, and a custom app store. With its Windows Phone 8 model, Lenovo would want to keep as much of the customized build as possible. Microsoft might give in with the app store, but allowing Lenovo to go ahead with customizing the UI will be a hard sell for the OEM.
source: WPDang (translated), WPSauce via WMPoweruser